The invention relates to a method for specifying a system to include a plurality of interconnected functional modules at respective hierarchical levels, each module representing a respective abstract state-based-machine. The modules may be hardware, and in particular, electronic modules, although this is not an absolute restriction. Alternatively, a module may be realized as a software module, or a composite of both hardware and software. In this same respect, the modules as a group may be realized in a uniform manner, or in a non-uniform manner. Each module behaves as an abstract state-based-machine, that has a plurality of states, but whereof the realization is still open to many options, and which therefore is called an abstract machine. By itself, an exemplary realization of such a state machine has been disclosed in U.S. Pat. No. 5,477,168 to the present assignee and herein incorporated by reference. Present-day computer-oriented hardware is rendered functional for a particular purpose only through specifying the workings thereof by an ever-increasing amount of appropriate software, that fits both to the hardware and to the intended application functionality. Generally, such software is of the multiprocessing type, inasmuch as this allows reusability of the various software modules, mutual interfacing between the modules on a manageable level of complexity, sharing of programming effort over multiple persons, and easier checking for errors. It has been found necessary to specify the various modules according to a straightforward methodology, in order to guarantee reliability, consistency, and maintainability. Relevant art has been presented by H. B. M. Jonkers, Overview of the SPRINT Method, Proceedings of the Formal Methods Europe Conference 1993 and published in Lecture Notes on Computer Science, No. 670, pp 403-427, Springer 1993. A basic language COLD is used therein for describing systems in an abstract manner without necessitating the specifying of an implementation. The SPRINT methodology allows for an easy way to subsequently implement such systems. However, for many environments the above methodology requires further optimization.